Crankcase filtration assemblies are widely known and used in a number of engine applications, such as engine aerosol and oil filtration. For example, during the combustion process in a spark ignited or compression ignition engine, compression gases and other byproducts of combustion may enter into an engine's crankcase. This condition is called blow-by. At this time, gas pressure develops in the crankcase that is above atmospheric pressure. Due to the pressure increase, the blow-by gases are ventilated from the engine crankcase through openings, which are usually located in a valve cover assembly or upper engine block area. These blow-by gases contain various particulate matter, odor, and toxic exhaust gases as crankcase emissions. When the crankcase ventilates into the surrounding environment it is known as open crankcase ventilation (OCV). Over time, the blow-by flow rate increases. As a result, a blow-by gas stream may be carrying an increased amount of particulate matter, odor, and toxic exhaust gases.
In general, crankcase ventilation filtration typically occurs through a process known as separation, for example through a coalescer element and/or impactor element. Generally, separation structures are configured to separate condensates from the blow-by gas stream. When a coalescer element is employed, smaller particles may be separated from the blow-by gas stream and coalesce into larger particles to help remove such particulate matter from the blow-by gas stream. To aid in the coalescing process, crankcase filtration assemblies often employ a media structure that collects the smaller particles. In the example of an impactor element, a structure is employed that gets in the way of, or impacts the blow-by gas stream to trap more coarse particulate matter.
Beginning in 2007, crankcase emissions have been counted toward total engine emission levels. In certain situations, the crankcase emissions from older and less maintained engines were found to contribute the majority of the total unregulated toxic emissions. Current emission control products for crankcases employ separation structures that are designed to mainly reduce coarse particulate matter (PM) emissions. Such PM emissions typically are mechanically generated with a size range of larger than 0.5 micron. While it is important to control large PM emission in order to reduce the total PM mass emissions, studies show crankcases emit significant amounts of chemically and thermally generated ultra-fine PM (about<0.5 micron), gases, odor, and unregulated toxic species.
Improvements may be made upon existing emission control products where crankcase gases are emitted to the atmosphere, and particularly in products for open crankcase ventilation systems.